In a line for tight flask molding, molds that are molded within flasks have cavities that face downward. Both the upper flask and the lower flask are turned over by means of a device for turning over the molds so that the cavities face upward. The upper mold is subject to operations such as scraping sand on the surface that is opposite the cavity, or forming a sprue, from underneath. The lower mold is subject to operations such as placing it on a molding board, or setting a core onto it. Then only the upper flask is turned over again by the device for turning over the molds, so that the cavity faces downward to be assembled on the lower flask. Thus conventionally a device for turning over the molds as in Patent Literature 1 has been used.
FIGS. 8 and 9 show a structure of a conventional device for turning over molds. As in FIG. 8, the device 101 is located on the middle of a conveyor 102 with stationary rollers. It has a turning over roller conveyor 104 that turns over a metal flask 103 on it and a pair of turning over wheels 105 that are attached to respective sides of the turning over roller conveyor 104. The outer surfaces of the pair of the turning over wheels 105 are supported by two pairs of supporting rollers 106 with flanges. A driving roller 109 is provided on one or both of the turning over wheels 105 so as to turn over both the turning over wheels 105 and the turning over roller conveyor 104.
Since the cycle time of the conventional line for tight flask molding is long, the flasks are slowly transported. Thus no serious problem has been generated by the device 101 for turning over the molds. However, in a recent line for tight flask molding, the cycle time has been shortened and the flasks are transported at a high speed. Because of the reaction caused by the transportation at the high speed, the turning over wheels 105 that are attached to the turning over roller conveyor 104 tend to move downstream. Thus the sides of the turning over wheels 105 and the flange of the supporting rollers 106 are quickly worn away.
As the cycle time is shorter, the speed for turning over a flask has increased. The tread surfaces of the pair of the turning over wheels 105 and those of the supporting rollers 106 with flanges are quickly worn away. This is a problem. To solve this problem, scrapers 111 for cleaning the tread surface are provided as in FIG. 9. However, they are fixed types. After they are worn away the effect for cleaning cannot be maintained. Thus frequent maintenance is required.
Further, since the device 101 for turning over the molds usually holds the flask 103 in it, the turning over wheels 105 cannot be easily replaced. The cost of the turning over wheels 105 is also high. An approach to enhance the resistance to wear of the turning over wheels 105 by changing the raw material or by means of a heat treatment may cause a significant increase in cost.
The present invention aims to solve the above-mentioned problems by providing a device for turning over molds that can reduce the wear of a turning over wheel and a supporting roller even when the speed for transporting a flask or the speed for turning it over increases to shorten the cycle time.